A distinction is generally made between rail-bound articulated vehicles such as streetcar trains or railroad trains and road-bound articulated vehicles such as articulated buses. The vehicle parts connected to one another in an articulated manner, for example vehicle parts of a rail vehicle or of an articulated bus have a passage that comprises at least one bellows that surrounds the floor of the passage and optionally also the articulation in a tunnel-like manner to enable persons to change from the one vehicle part to the other vehicle part over the floor without said persons being exposed to weather influences. It must be noted in this connection that the bellows are formed as folding bellows or as wave bellows, with wave bellows in particular being used in rail-bound vehicles and folding bellows in particular being used in articulated buses.
In rail-bound vehicles such as in particular railroad trains, the floor is configured as a link bridge, for example. Such link bridges are sufficiently known from the prior art. It is furthermore also known to configure the floor as a platform, with the use of platforms typically being known with articulated buses. There is in particular now the demand with rail-bound vehicles that the floor of the passage, for example a link bridge, has a certain resistance to the effect of fire in the region of the passage. This means that a specific temperature should not be exceeded over a specific time period at the upper side of the floor of the passage.
It has already been initially pointed out that the bellows surrounds the floor of the passage in a tunnel-like manner; that is, the floor of the passage is also covered by the bellows at the lower side. The bellows thus forms a tube. This means that the floor region of the bellows is located below the floor of the passage, for example, of a link bridge. An origin of a fire is now below the floor region of the bellows so that the floor of the passage is not directly exposed to fire. It becomes clear from this that the heating of the floor of the passage can be delayed for a specific time period, at least in the floor region of the bellows, by a fire-retardant design of the bellows.
The design of a bellows is known in this connection, for example, from DE 20 2015 105 102 U1, wherein an outer strength layer is provided on which a flame-protective layer is arranged at the inner side. A further strength layer can in turn be arranged on this flame-protective layer.
A two-layer design of a bellows is known from EP 1990563 A1 wherein the individual folds or waves of such a bellows have an outer jacket and an inner jacket, that are arranged spaced apart from one another, for forming a two-layer structure. Provision is made in this respect to arrange a fire-protective layer of intumescent material between the inner jacket and the outer jacket. Good results with respect to a delayed heating at the upper side of the floor of the passage have already been achieved using such a design of the bellows, in particular of the bellows bottom.
However, the demands on fire protection have been increased in recent years, with in particular the time period within which a specific temperature at the upper side of the floor of the passage may not be exceeded having been increased.